PC slot card modems are generally required to operate at 3.3 volts (dc) ±10% for a rough range of 3.0 to 3.6 Vdc. Typical Power amplifier devices on the market, however, are optimized to work using a lithium ion battery that has a nominal voltage of 3.6 Vdc and an end-of-life at 3.2 Vdc. For a given power amplifier, its maximum output power with good spectral characteristics is a function of operating temperature, operating frequency, and operating voltage.Po(max)=f{t, f, v}
The operating parameters of the power amplifier may vary with ambient conditions, supply voltage, and what part of the allocated cellular frequency band is currently being used. Typically, a wireless carrier will specify the nominal, minimum, and maximum output power they want for wireless devices on their network since the power amplifier's output directly affects the communication range between the nearest network basestation and the wireless device. RF power output is typically maintained at a nominal level of +28 dbm +/−3 dbm for instance. A problem arises when one or more of the operating conditions exceeds the power amplifier's optimal operating range while the power output is maintained at nominal or higher levels. In such cases the power amplifier RF spectral response begins to degrade in quality and, if left to continue, may degrade to the point that useful communications are compromised.
Often if the RF power output were allowed to be reduced even slightly, then the RF spectral response between the wireless device and the nearest basestation can be maintained at acceptable levels with a minimal impact to the effective range of the wireless device.
Common engineering practice today is to set the nominal RF output power lower than the power amplifier's capability at nominal operating conditions to allow for further degradation at the worst case operating condition extremes. Since the operating condition extreme exists only a small percentage of the total time a cellular terminal is in use, the RF output power is unnecessarily controlled to lower than optimal levels most of the time.
What is needed is an intelligent monitoring and adjustment system that can monitor and incrementally adjust the RF power output of the power amplifier to continuously maintain the maximum output achievable while assuring good RF spectral performance.